In a 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) system, a user equipment (UE) which receives data over a physical downlink shared channel (PDSCH) operates according to one of several transmission modes. The transmission mode defines rules for transmitting data between a base station (eNB) and a UE. In the existing 3GPP LTE standard, seven transmission modes of (1) port 0 single-antenna port transmission, (2) transmit diversity, (3) open-loop spatial multiplexing, (4) closed-loop spatial multiplexing, (5) multi-user multiple input multiple output (MU-MIMO), (6) closed-loop rank 1 precoding and (7) port 5 single-antenna port transmission are defined. The transmission modes are UE-specifically or semi-statistically set.
In association with the transmission mode, an antenna configuration of an eNB (or a cell) is defined. The antenna configuration may be, for example, information about the number of antenna ports. The antenna configuration may be cell-specifically set. A UE may determine an antenna configuration of an eNB by reception of a physical broadcast channel (PBCH) from the eNB.
The PBCH is a control channel for transmitting system information such as a downlink system bandwidth and a system frame number (SFN). However, an antenna configuration is not explicitly included in a message transmitted on the PBCH. Accordingly, a UE should blind detect the antenna configuration of an eNB using the PBCH. More specifically, the UE may perform blind detection by decoding the message on the PBCH according to different MIMO transmission schemes (single antenna, space frequency block coding (SFBC) and SFBC-frequency switched transmit diversity (FSTD)) corresponding to various numbers of transmission antennas (for example, 1, 2, or 4 transmission antennas) of the eNB.
A cyclic redundancy check (CRC) bit of the message on the PBCH is masked with a bit stream indicating the number of transmission antennas. Accordingly, the UE may reliably detect the number of transmission antennas of the eNB by checking the CRC of the message transmitted on the PBCH in addition to the above-described blind detection.
According to the method of blind detecting the number of transmission antennas of the eNB, since a decoding process needs to be performed at least three times according to three antenna configurations and the PBCH is repeatedly transmitted four times in a time domain, the UE must perform blind decoding a maximum of 12 times in order to acquire the antenna configuration of the eNB.
In addition, in the existing 3GPP LTE system (including Release 8 and 9), 1-, 2- or 4-Tx antenna configuration is defined in downlink transmission. However, in the 3GPP LTE-A (Advanced) system, an eNB may support a maximum of eight transmission antennas in downlink transmission. In the 3GPP LTE-A system, a UE based on the existing 3GPP LTE standard and a UE based on the 3GPP LTE-A standard need to accurately acquire information about a transmission antenna configuration of an eNB. The UE based on the existing 3GPP LTE standard may recognize eight transmission antennas of the eNB as four transmission antennas using an antenna virtualization scheme for grouping the eight transmission antennas two antennas by two antennas. Meanwhile, the UE based on the 3GPP LTE-A standard also operates to acquire transmission antenna configuration information of the eNB through the same blind detection as the existing 3GPP LTE standard and CRC. However, currently, in the 3GPP LTE standard, since a method of accurately informing a UE that the number of transmission antennas of the eNB is eight is not defined, even when the eNB has eight transmission antennas, the UE misrecognizes that the number of transmission antennas of the eNB is less than 8.